Lewis & Short

sollistĭmus (sōlist-), a, um, adj. [old sup. form of sollus = salvus; v. Corss. Krit. Beitr. p. 313 sq.], most perfect, only in the expression tripudium sollistimum, in augural lang.; the most favorable omen, when the chickens ate so greedily that the corn fell from their bills to the ground, Fest. p. 298 Müll.; Cic. Div. 1, 15, 28; 2, 34, 72; Liv. 10, 40; cf. Becker, Antiq. II. pt. 3, p. 79; and Lange, Antiq. I. p. 257.